Air liquification systems are known wherein a high energy fuel, such as hydrogen, is stored in a liquid state and burned in a gaseous state. The liquid hydrogen is used in a condenser for converting ambient air to a liquid state. During the condensing process, the liquid hydrogen is converted into a gaseous state for use with the combustor. The liquid air, in turn, is fed to the combustor for mixing with the gaseous hydrogen.
In some schemes, two combustors are utilized wherein one combustor operates at greater than ambient pressure and a second combustor operates at ambient pressure. In such schemes, a portion of the liquid hydrogen is conducted directly to the high pressure combustor for mixing with the liquid air. Ambient air is fed directly to the low pressure combustor for mixing with the remainder of the hydrogen which has been converted to a gaseous state in the process of liquifying the air.
A major problem with systems as described above, such as in an aircraft propulsion engine, is that the ratio of the mass flow of air to the mass flow of liquid hydrogen used to generate the high pressure air has been insufficient, with the result that overall propulsion efficiencies are low. It would be desirable to provide an improved system wherein the amount of air liquified per unit of hydrogen is significantly increased. This invention is directed to solving the above problems and satisfying such needs.